193nm film with low loss and high reflectivity and its preparation method

Abstract

The provided is a 193 nm film with low loss and high reflectivity and its preparation method, including a substrate and a film deposited on the substrate; the film structure is Sub/(HL){circumflex over ( )}n/Air, wherein Sub is the substrate of the film element, Air is the outgoing medium air, H and L are the high refractive index material film layer and the low refractive index material film layer with ¼ central wavelength optical thickness respectively, and n is the number of film stacks of high and low refractive index materials. The provided adopts the above-mentioned 193 nm film with low loss and high reflectivity and its preparation method, which can effectively inhibit the crystallization of LaF3 film in 193 nm high reflective film, thereby reducing the roughness of the reflective film, inhibiting the scattering loss, and improving the reflectivity of the film.

What is claimed is: 
     
         1 . A preparation method for a 193 nm film, comprising a substrate and a film, the film is deposited on the substrate; a film structure is Sub/(HL) {circumflex over ( )}n /Air, wherein Sub is a substrate of a film element, Air is an outgoing medium air, H and L are a high refractive index material film layer and a low refractive index material film layer with ¼ central wavelength optical thickness (in nm) respectively, and n is a number of film stacks of high and low refractive index materials;
 the high refractive index material film layer His a LaF 3 -AlF 3  mixed film, and the low refractive index material film layer L is an AlF 3  film; 
 wherein the preparation method comprises the following steps: 
 S 1 , selecting an electron beam evaporation deposition equipment and the substrate, and adding a crystal oscillator thickness monitor to symmetrical positions on both sides of a coating cavity of the electron beam evaporation deposition equipment; 
 S 2 , preparing the high refractive index material film layer H, setting a LaF 3  side corresponding to a crystal oscillator monitoring rate of 0.7 nm/s, setting a first AlF 3  side corresponding to a crystal oscillator monitoring rate of 0.3 nm/s; 
 opening LaF 3  side and AlF 3  side baffles at the same time during evaporation, depositing the LaF 3 -AlF 3  mixed film by using a dual-source electron beam co-evaporation deposition process, and controlling a film thickness by using a time monitoring; 
 in S 2 , a physical thickness (in nm) of the high refractive index material film layer H is expressed as 48.25/(0.7 nH+0.3 nL), wherein nH is a refractive index of LaF 3  and nL is a refractive index of AlF 3 ; 
 S 3 , preparing the low refractive index material film layer L, setting a second AlF 3  side corresponding to the crystal oscillator monitoring rate of 0.3 nm/s, and using crystal oscillator monitoring to control the film thickness; 
 in S 3 , a physical thickness (in nm) of the low refractive index material film layer L is expressed as 48.25/n, wherein n is a refractive index of the low refractive index material film layer L; 
 S 4 , alternately depositing the high refractive index material film layer H and the low refractive index material film layer L until the film structure is plated to obtain a La 0.70 Al 0.30 F 3 /AlF 3  film, wherein in the dual-source electron beam co-evaporation deposition process, a substrate temperature is 150-250° C., and a vacuum degree is less than 1.8×10 −4  Pa. 
 
     
     
         2 . The preparation method for the 193 nm film according to  claim 1 , wherein a central wavelength of the film is 193 nm, the number of film stacks is 18-30. 
     
     
         3 . The preparation method for the 193 nm film according to  claim 1 , wherein a substrate material is fused silica, and a roughness is less than 0.5 nm. 
     
     
         4 . The preparation method for the 193 nm film according to  claim 1 , wherein a spatial position of the crystal oscillator thickness monitor is lower than a workpiece plate. 
     
     
         5 . (canceled)